Grinding method



Patented June 20, 1950 GRINDING METHOD Howard W. Meyer, Indianapolis,Ind., assignor, by mesne assignments, to The Marquette Metal ProductsCompany, Cleveland, Ohio, a corporation of Ohio Application April 9,1948, Serial N 0. 19,972

4 Claims. 1

The present invention is concerned with a means and method for finishingthe outer diameter of certain members of an assembled group of parts ona lathe or grinding machine.

In the manufacture of a spring clutch assembly incorporating a sleeve orhub member on which is mounted a clutch spring and a pair of flankingbearing members, difiiculty has been encountered in maintaining thenecessary tolerances and concentricity in the unit after assembly. Whenthe separate parts of the assembly are finished before being assembled,the unit may reflect an accumulation of tolerances, allowable so far asthe individual parts are concerned, but resulting in undesirablerelative eccentricity of parts or sub-assemblies in the finished unit.Heretoi'ore it Was considered impracticable to grind the bearingsurfaces after assembly of the unit, since some of the coils of thespring incorporated therein had a larger outer diameter than the bearingsurfaces to be finished and further the spring was free-floatingradially about the hub or sleeve member so that it would necessarily bein the way of a grinding or cutting tool as well as suffer possibledamage to its finished surface were such an operation attempted.

An object of the present invention is to pro- A further object of theinvention is to provide a fixture as described above which may beinexpensively and easily fabricated and in use will facilitate suchoperation as outlined above, requiring a minimum of time and labor.

Another object is to provide a method for grinding or cutting a surfaceon a plural assembly as described which will provide a finished surfaceof required concentricity within required tolerances while saving bothlabor and time.

In the drawing, Fig. 1 is a side elevation of the fixture employed forpracticing the invention; Fig. 2 is a side elevation of an assembly suchas the method and fixture ofthe present invention is designed to handle;Fig. 3 is a diagrammatic view showing the plural assembly mounted in thefixture for the finishing operation.

With reference to the drawing, the fixture comprises a bed plate I towhich vertical standards or brackets 2, l0 and 20 are rigidly attachedin a common vertical plane. A generally horizontal arm 3 is pivoted at 4to the top end of the largest bracket 2. A free turning roller 5 ismounted at the free end of arm 3 for engaging one portion of the workconstituted by the spring clutch assembly. A rod 6 extends through thearm 3 between its ends, depends therefrom and has a spring 1 bearingdownwardly on the arm and holding the arm against a shoulder 8 on therod below the arm. The vertical bracket It has a free turning roller llmounted on its upper free end. A horizontal arm [2 extends rigidly fromthe bracket [0 and is screwthreaded for receiving companion threads onthe lower end of rod 6. The third vertical bracket 29 has a free turningroller 2| mounted on its upper end. All the rollers are also in a commonvertical plane.

Arm 3 may be swung vertically, within the limits of the spring-biasedconnection I, 8 to move roller 5 with reference to the position of thefixed rollers II and 2| to allow the work to be moved into place inengagement with the three rollers. The normal position of roller 5 maybe adjusted through the threaded connection of rod 6 with member l2, tocontrol the pressure of roller 5 on the work and allow for variation inthe diametral size of the work.

As an example of the type of work for which the present method and meanswas devised, a spring clutch helix assembly is illustrated in Fig. 2.This assembly comprises a hub or sleeve A having a circular fiange Bformed thereon, the inner axially disposed face thereof being of helicalform complementary to the adjacent end of a helical clutch spring C. Thespring is connected to flange B by means of a toe C on the springengaging a radial slot in the flange. Bushings or bearing members D areconcentrically mounted on sleeve A at its ends. The spring C has amaterially larger inner diameter than the outer diameter of sleeve A sothat it is substantially in a radially free-floating condition, looselyaround the sleeve A.

The assembly described above is intended for insertion within an axialbore of a gear indicated in broken lines at G in Fig. 2 for freerotation relative thereto in one direction. Sleeve A is secured to ashaft whereby torque may be transmitted from the gear to the shaftthrough the spring clutch assembly. The outer peripheral surface of thespring is designed for grip-i ping frictional engagement with the drumsurface formed by the axial bore of the gear whenever the gear is turnedin its normal driving direction. Since the device is intended for highspeed operation, all the parts thereof must be finished to closetolerances and concentricity of the bearing surfacesbetween members Dand the gear member is necessary to prevent vibration and otherundesirable conditions.

To satisfy the requirements mentioned above it is desirable that thesurfaces of bearing members D be ground or finished at the same time andwhile mounted on the helix sleeve A and after the unit is thus assembledso that the inner diameter of the hub or sleeve A will-beexactlyconcentric with the outer diameter or bearing surface of the members D.Since some ofthe coils, energizing coils E, of spring C have a largerouter diameter when relaxed than the outer diameter of f the bearings Dand the entire clutch spring is loosely mountedon sleeve A between theprojectingbearings, performance of such an operation by the usualmethodswould be impossible without doing damage to the accurately machinedclutching surface of the spring.

Whenthe peripheral surfaces of the helix as. sembly are to be ground ona grinding machine, sleeve A with spring C and bearing members Dassembled thereon, is mounted on an arbor 39 (Fig. 3) of the samediameter as the shaft on which the assembly is finally to be mounted.The arbor is then secured in centers supported on a traversing carriagefor movement parallel to the axis of the grinding-wheel movable forcross-feed movement in a direction at right angles to thecarriagetraversing movement for determining the radial dimension of the finishedsurface. The fixture l etc. of this inventionismounted on themovablecarriage in fixed relation to the center supporting arbor Siiand in suchposition that its rollers 5, Il and El. will make three-region contactwith spring C, as shown diagrammatically in Fig. 3. Arm 3 and roller 5may be retracted, asby hand, while the assembly A through E is beinglocated on the arbor 3ll'and itssupporting:centers, rollers ii and 2;!supportingly engaging the periphery of spring C between the members Dand out of contact therewith. Release of arm 3 bringsroller dintocontact with the periphery of the spring. All of the rollers being ofawidth-somewhat less than the total length ofspring C, they will enter between the members D to urge the inner suriaceof the spring toward oragainst the periphery of sleeve A. v l The fixture with its rollers isso arranged and mounted upon the traversing carriage that the axis ofthe spring engagedby the rollers, i. e. the center of the circle definedby the three rollers, is eccentric of the center of the axis or centerof sleeve A orin other words of the axis of the arbor upon which thesleeve is mounted and its supporting centers. By thus supporting thespring eccentrically of the bearing members D being worked upon, thesurface region of the spring adjacent the grinding wheel isprogressively held in spaced relation to the surface of the bearings atthe point where the working tool contacts.

As iscustomary in grinding machinesof this type, the arb'or 39' isrotated on its Supporting centers for finishing the circumferentialsurface of the bearing members D. If the inner surface of them'aincoilof the spring is held against the surface of sleeve A in theoppositedirection from the working tool, it will also be rotatedeccentrically of the bearings and. with its outer peripheral surfaceclear of the grinding wheel. The traversing carriage is moved to bringfirst one and. then the other of the members D into contact with thegrinding wheel, which is moved at right angles thereto for grinding thesurfaces to the proper radial dimension, all in the usualapprovedmanner, so that the surfaces-L of the members D may be precisionfinished within allowable tolerances and. concentrically of the bore ofsleeve A after final assembly, with the same precision and facilitya'swould be possible if the spring were not mounted'on' the assembly, andwithout damage to the spring;s -surface.

The method and means described above may be employed" -rc1--- finishingvarious assemblies where a similar problem is presented. In some casesthe tubular member corresponding to the spring-Q-E may be free to rotaterelative to the inner supporting member, in which case the rollers maybereplaced by non-rotating. engaging members and the innerbody allowedtorotate within and-independently of the tubular memher so engaged:

I claim:-

1. In peripherally machining one of. two per-- manently locse coupledbut normally concentriccircular parts the method of protecting the:otherpart against damage by a tool: comprising. sup-' 2 porting. suchonepart on a fixed center for presentation to the tool and supportinglyengaging. the periphery of other part at opposite sides of the region--of operation of the tool: and at: regions spaced apart circumterentiallyofsa'id other par-17,. the regions ofengagementbeing: so located. as to:

maintain said other' par-t continuously eccentric relative to said one 7part 2 The method of machining the peripheral surface ofa protrudingflange-member ona generally. circular body forming apart of a pluralassembly includinga tubular member carriedpermanently but loosely onsaid body adjacent said flange member comprising. mounting said body: ona fixed. axis for rotatably presentingthe surface to bemachined to-a.rnacliin'ing tool, and" meanwhile engagingthe surface'of said tubularmember at a plurality of circumferentiallyspaced regions arounditsperiphery and so' located as to hold the axis-ofthe tubular membereccentrically of the body to be machined-ma direction: away fromthe Yregion of operationor said tool;

3. The method": oi. machining the peripheral surfaces of protrudingflange members carriedby a generally cylindrical body forminga part 1;of a pluralasse'mbly including a tubular member freely mounted onsaid=body between said flange members and having an outer diameter atleast as great as thatofthe surface t'o'be machined; comprisingmounting. said body on a fixed axis for: rotatably presentingthesurfaces to bema'ci'lined to a machining t'o'ol,- engaging the'surfa'ce of saidfreely mounted tubular 'm'ember'at spaced regions aboutit's periphery so located that the tubular member is maintainedeccentrically of said fixedaxis in a direction away irom' the point ofengagement of said tool'with the surface tcbe machined; and effectingrotation of saidbody'within said tubular member.

4. The method of machining the peripheral surfaces of protruding fiangemembers carriedby a generally cylindrical body forming a part of aplural: assembly including a tubularmember freely mounted on said bodybetween said fi'ange members; comprising mounting said body u on a;rotatable arbor positioned to present the surface of the flange memberscarried thereby to a machining tool, engaging the peripheral surface ofsaid freely mounted tubular member by fixed rollers positioned atintervals about its periphery,

said rollers being located with the center of the 5 circle definedthereby eccentrically ofiset with respect to the axis of said rotatablearbor in a direction opposite the point of engagement of said surfaceand said machining tool, whereby said cylindrical body and said tubularmember will rotate together and on eccentric axes so that the surface ofsaid flange members and the surface of said tubular member will beoffset at said point of engagement. HOWARD W. MEYER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

